Centrifugal pump for high temperature liquids



y 4, 1954 E. F. VITEK 2,677,328

CENTRIFUGAL PUMP FOR HIGH TEMPERATURE LIQUIDS Filed Dec. 30, 1949 3Sheets-Sheet 1 F@./.

Inventor:

by Z M His Attorney Edwahd F. ViteK,

May 4, 1954 E. F. VITEK CENTRIFUGAL pum FOR HIGH TEMPERATURE LIQUIDS 3Sheets-Sheet 2 Filed Dec. 30, 1 949 Inventor: Edward F. Vite by HisAttorney.

May 4, 1954. E. F. VITEK 2,677,328

CENTRIFUGAL PUMP FOR HIGH TEMPERATURE LIQUIDS Filed Dec. 50. 1949 Fig.3.

3 Sheets-Sheet 3 Inventor: Edward FiVitek,

by 4f M His Attovney Patented May 4, 1954 CENTRIFUGAL PUMP FOR HIGHTEMPERATURE LIQUIDS Edward F. Vitek, Schenectady, N. Y., assignor toGeneral Electric Company, a corporation of New York Application December30, 1949, Serial No. 135,997

2 Claims. 1

This invention relates to a centrifugal pump especially adapted forhandling unstable, corrosive, or otherwise dangerous liquids atextremely high temperatures, on the Order of 800 F.

The object of the invention is to provide an improved centrifugal pumpof the type described which is fully protected against leakage of theliquid being pumped yet at the same time is so arranged as to facilitateaccess to the pump casing and impeller for inspection and servicing.

Another object is to provide an improved high temperature pumpconstruction having a novel combination of sealing and cooling means forpre venting leakage of the liquid being pumped at the place where thepump shaft projects through the casing, while at the same time reducingthe transfer of heat along the pump shaft and safely dissipating whatheat is conducted therealong.

Other objects and advantages will be apparent from the followingdescription taken in connection with the accompanying drawings, in whichFig. 1 is a vertical sectional view of the complete pump assembly; Fig.2 is a top view of the pump assembly of Fig. 1; Fig. 3 is an enlargedsectional view of the shaft sealing and cooling assembly;

and Fig. 4 is a plan view of a shaft seal and packing assembly taken onthe plane 4-4 in Fig. 3.

Referring now more particularly to Fig. 1, this improved pump assemblyconsists of a motor indicated generally at l bolted to the top of amotor stand 2, the bottom end of which is secured by bolts to a "floorplate 3, which forms the main frame member of the assembly. The shaft ofmotor I is secured by a suitable flexible coupling i to a pump impellershaft 5 carried in; a pair of suitable axially spaced anti-frictionbearings shown generally at 6, 'l. The structural details of thecoupling 4 and bearings t, i are not material to an understanding of thepresent invention and are therefore not described more particularlyhereinafter. Associated with the central opening in the floor plate 3through which the shaft 5 projects, is a packing and cooling assemblyindicated generally at 8, the details of which will be described moreparticularly hereinafter in connection with Fig. 3.

The frame and housing assembly of the centrifugal pump proper consistsof three main components. Secured to the under side of the floor plate 3by a circumferential row of studs 9 is'a pump frame member 10, which iscylindrical in shape with a lower end portion defining a circumferentialflange II to which the discharge scroll casing i2 is secured by aplurality of circumferentially spaced studs 8. Projecting radially 2inward from the flange II is a wall or web portion [4 carrying a centralcylindrical portion 15, which forms the housing for a shaft coolingarrangement described more particularly hereinafter.

Secured to the bottom of the discharge scroll l2 by a circumferentialrow of threaded fastenings i6 is the pump intake casing indicatedgenerally at I1 as being an elbow-shaped pipe having at the pump end aflange [8 forming a closure for the bottom of the pump casing, andhaving at the other end an intake conduit flange lg to which is boltedthe intake pipe 20. As will be apparent from Fig. 1, suction pipe 20turns upwardly and projects through an opening 2| in the floor plate.This opening is substantially larger in diameter than the suction pipe20, the intervening annular space being closed by a flexible joint 22comprising an annular member Eta of U-shaped cross-section welded at itsouter edge to the circumference of the opening 2i in the door plate, theinner circumference being welded to a collar 22b which is in turn weldedto the outside of the pipe 20. This flexible joint is provided so thatdifferential thermal expansion between the conduits, pump casing, andfloor plate, may be accompanied by transverse shifting of the conduit 20within the opening 2! without imposing unduestresses on any of thecomponents.

As will be obvious from Fig. 1, the conventional centrifugal impeller 23is secured by impeller nut 24 to the reduced end portion of shaft 5. Thedischarge scroll l2 terminates at a discharge flange 25a,- to which issecured by bolts 25 a flanged discharge elbow 2t. Conduit 26 likewiseprojects upwardly through an opening in the floor plate 3 and is sealedthereto by an annular flexible member similar to the ring 22a. Therelation of the suction and discharge pipes may be seen more clearlyfrom the top view of Fig. 2,

the flexible sealing ring for the discharge'pipe being indicated at 21.r p

Since in handling dangerous liquids of the type for which the presentpump was designed it is necessary to be able to completely drain thewhole system, special valved drain conduits are provided for the intakeand discharge pipes. The lowermost portion of the U-shaped bend'in theintake pipe is provided with a drain tube 21 with a valve shownin dottedlines at 28. Similarly, the lowermost part of the discharge conduit 28is provided with a drain tube 29 having a suitablevalve 30. Asmay beseen in Fig; 2, the drain conduits 21,29 simply discharge into theenclosing casing 3 l .j as may bes'ee'n in Fig. 1, this outer 3 tank 3|is imperforate except for a single drain port communicating with conduit32, which may deliver to a suitable closed storage tank showndiagrammatically at 320..

In order that the drain valves 28, may be operated from outside theenclosure defined by the floor plate 3 and tank 3|, suitable operatingextensions are provided for the hand wheels of the valves. One suchextension is shown diagrammatically in Fig. 1 in the form Of anactuating rod having at the lower end thereof a yoke 36 adapted toengage the spokes of the hand wheel 30a. The upper end of rod 35 passesthrough a suitable stuffing box 31 and carries an actuating hand wheel38.

It will be seen in Fig. 1 that the cylindrical casing 3| is providedwith a bolting flange 33 by which it is tightly secured to the bottomsurface of the floor plate 3 with a suitable fluid sealing gasket 34between. Thus it will be ap-' parent that any leakage from the pumpcasing, for instance through the gaskets Ha, |2a at either side of thedischarge scroll l2, or past the gaskets at the flanged suction jointI9, or the intentional leakage of cooling fluid described hereinafter,will all be collected in the bottom of tank 3| and drained throughconduit 32. It will also be observed that this arrangement of the pumppermits the suction and discharge conduits 20, 26 to be securely weldedat the exterior side of floor plate 3 into the piping system with whichthe pump is associated. Thus the system for circulating a potentiallydangerous liquid may be almost completely sealed by welded joints, allthe bolted flanged joints with gaskets being located within the leakagecollecting tank 3|. At the same time, access to the pump is madepossible simply by removing the tank 3|, unbolting the intake flange |9and removing the inlet elbow H by removing the bolts Hi. This gives freeaccess to the impeller 23, which may be removed from the dischargescroll |2 simply by removing nut 24.

In order to prevent contamination of the liquid by oxides or otherdecomposition products resulting from contact with the air, the tank 3|is pressurized with a suitable inert gas, as illustrateddiagrammatically by a storage bottle 3|a from which an inert gas such asnitrogen is supplied by conduit 3|b having a pressure regulating valve3|c adapted to maintain the gas pressure within the tank 3| at about 5to 15 pounds per square inch, gage. This insures that there will be noinfiltration of air from the leakage path which might exist through thegasket 34, etc.

Because of the dangerous nature of the liquids to be pumped, and thefact that they are at an extremely high temperature, it is necessary tomake absolutely sure that there is no leakage from the pump enclosure,and that the transfer of heat from the hot liquid along the shaft to thebearings is prevented, since anti-friction bearings cannot operate overlong periods at temperatures much in excess of 300 F. The various meansfor preventing this transfer of heat and eliminating the possibility ofleakage are as follows.

In order to prevent the transfer of heat by radiation from the pumpcasing to the floor plate 3, a plurality of spaced radiation shields areprovided, in the form of annular plates 39 .secured by machine screws 40to the floor plate 3 with suitable washers between so that there ambientatmosphere through any.

4 is an air space between the respective radiation shields and betweenthe shields and the floor plate. These shield plates are preferablyhighly polished on both sides in order to resist the transfer of heat byradiation. As may be better seen in Fig. 3, a similar radiation shieldassembly is secured to the floor plate 3 within the cylindrical memberI0. This inner shield assembly is indicated generally at 4|. Thisradiation shield arrangement is found to be so effective that the floorplate may be left without heat insulation on the exposed top surfacethereof, for convenience of access for inspection of the various valves,packing assemblies, flexible joints, etc. associated with the floorplate.

The first barrier to the conduction of heat along the impeller shaft 5is in the form of a cooling coil contained within the cylindrical memberI5 and having helical cooling passages 42a machined in the bore of acylindrical bushing 42. At its lower end, bushing 42 is provided with anannular lip 43 defining a close clearance 43a with the shaft. Similarlyat its upper end, the bushing 42 is provided with a lip 44 forming aclose clearance 44a. These clearances are made as small as practicable,consistent with the necessity for preventing mechanical interferencewith the shaft. This is a difficult problem since, with a single outletimpeller of this type, the hydraulic forces on the impeller deflect theshaft sideways, with the result that the clearances 43a, 44a must be onthe order of .012 inch with a shaft diameter of 2% inches. The coolantused is a portion of the liquid being pumped taken from the dischargeconduit, as for instance by the conduit 45, whence it passes through asuitable air-cooled heat exchanger indicated diagrammatically at 46,from which the cooled liquid passes through a conduit 41. Conduit 41 iscoupled by a pipe union 48 with another conduit 49 welded into a flangeat the top of cylindrical member |5. Conduit 49 communicates by way ofport 50 with the upper end of the helical cooling passage 42a.

It will be obvious that the comparatively cool liquid in cooling passage42a readily extracts any heat which may be conducted along the shaft.Spent coolant is discharged through the clearance 43a into the annularchamber 5| defined between the lower end of cylindrical member i5 andthe adjacent surface of impeller 23. This coolant fluid may readily passthrough the pressure balancing holes 23a in the impeller into the fluidpumping passages thereof. It will be obvious that some cooling fluidalso escapes upwardly through the clearance 44a. To prevent this liquidcreeping up the shaft toward the sealing means described hereinafter, acentrifugal slinger disk 52 is threaded or otherwise secured to theshaft. It will be apparent that any leakage fluid passing through theclearance 440. will be thrown radially outward in the manner indicatedby the arrow 53 in Fig. 1. This liquid will run down the inside of thecylinder Ill and drain through one or more ports 54. As indicated above,this spent coolant fluid is collected in the bottom of the tank 3| andremoved through the drain line 32.

Surrounding the shaft immediately above the cooling coil, is a complexsealing and cooling assembly 8, the details of which may be seen byreference to Fig. 3.

As shown in the enlarged section of Fig. 3, the central opening in thefloor plate is closed by an annularplate member 55, whichis actuallyfabricated in two portions, the lower one a having a circumferentialportion adapted to be secured between the floor plate 3 and the boltingflange of housing portion Ill by the threaded fastenings 9. It will beapparent that the multiple radiation shields 4| are secured to thislower plate member 55a. Welded to the lower plate 55a is an upper platemember 55b having an annular recess 56 machined in its lower surface.This cooperates with plate 550. to form coolant passages, to whichcooling fluid is admitted through an inlet conduit 51 and exhaustedthrough conduit 58. The function of this cooling channel is of course tomake doubly surethat heat from the pump assembly will not be transferredby radiation and conduction throughthe comparatively heavy sections ofthe housing to the housing portion enclosing the shaft seal assembly.

The plate member 5517 has an upwardly extending flanged cylindricalportion 550 defining a stepped internal bore 59 closed by a top plate 60secured in place by a plurality of circumferentially spaced threadedfastenings 61. A suitable high temperature gasket 62 is located in anannular recess in plate ti! and clamped against the upper surface of theend flange of member 55c by the threaded fastenings 6i.

Carried on shaft '5', and secured thereto by means of a threaded portion5a with a lock. washer 5b is a sealing sleeve member 63 having a centralannular recess in which is located a resilient ring '65 for preventingleakage through the threaded joint, and a depending cylindrical skirtportion 65 of an inside diameter such as to be spaced a substantialdistance radially from the surface of the shaft. Into this spaceprojects cylindrical shield member 66' welded at its lower end to thecircumference of the central shaft opening in plate member 55b. Theshield 66 cooperates with the bore portion 59a to define an annulardrain chamber 51 communicating by way of a port 68 with a drain conduit69 having a valve "i5. Threadedly secured to the extreme lower end ofskirt portion Eli is a nut H which engages a spacer ring 12, which inturn retains a rotating seal ring '23 in place against a shoulder 14.Both the upper and lower annular surfaces of seal ring '13 are carefullyfinished, as by a suitable lapping process, to have extremely smooth andperfectly flat surfaces. Cooperating with these fiat sealing surfaces onthe rotating ring 13 are an upper and a lower sealing assembly. Theseare indicated generally at 15, Hi and the precise mechanical details ofthese seal assemblies are not material to an understanding of thepresent invention. However, for purposes of illustration, the lowerassembly 'l-Sis represented diagrammatically as consisting of an innercylinder ll having an upper flanged end portion '58 arranged intelescopic relation with an outer sleeve member it. Sleeve 19 hasan'inwardly extending flange E-G defining an upper and" lower annularchamber between the sleeves ll, 19. The'upper chamber houses one or morespring members, indicated as being a coil spring 81, which is arrangedto bias the inner sleeve "upwardly relative to the outer sleeve 19. Thelower chamber,- below the flange 89, houses suitable fluid sealingmembers, indicateddiagrammatically as being a pair of resilient rings82, which are'of course made of a suitable temperature resistingmaterial and are of such a size and shapeas'to be compressed somewhat soas to be in good fluid" sealing engagement with both inner and" outersleeves. The flanged end portion it of theinner' sleeve defines anannular recess in which islocateda carbon packing ring 83 biasedupwardly by spring 8| into sealing engagement with the lower lappedsurface of the rotating sealing ring 13. Thus it will be apparent thatresilient rings 82 prevent fluid leakage between inner sleeve 1! andadjacent stationary members, while'the' rubbing ring 83' preventsleakage between sleeve ll and the adjacent ring 13. Friction between thesealing rings 82' and the sleeves H, Hlmay be relied on to prevent theinner sleeve H and the" stationary packing ring 83 from rotating, orany'suitable' interlocking or key arrangement (not shown) between rings11, 19 may be provided. The upper seal assembly may be similar inconstruction and has a carbon ring, the projecting end portion of whichis shown' at 125a, contacting the up per lapped surface of the rotatingring l3.

The flanged housing portion 550, the topclosure plate 60, the rotatingring 13, and the two seal assemblies 15, 16 define a closed annularspace 8 to which a suitable cooling, sealing, and lubricating oil issupplied byway of an inlet conduit 85. This oil serves not only tolubricate the rubbing surfaces of seal ring 13, but is supplied in suchquantity as to give an appreciable cooling action. The principal portionof this cooling oil leaves-through an exit conduit 85a, but some findsits way between the respective carbon packing rings 15a, 83 so astolubricate'their rubbing engagement with the rotating ring 13'. Thatoil which leaks past the upper ring 75a escapes through the annularclearance space between seal assembly 75 and the member 63 and flowsradially outward overthe upper surface of top plate 60 and drops intothe annular space de' fined between the flange 55c and the lower endportion of the motor stand 2. This leakage may be permitted to drainaway through one or more holes or grooves 86 formed in the lower endface of the mounting flange of motor stand 2.

The lubricating oil which leaksbetween the rubbing surfaces of ring 13and the lower carbon ring 83 drains downwardly through the an-- nularspace between the inner sealed ring Ti and the nut H and collects in thedrain space 61. Periodically, this leakage can be blown out of the space61 by opening the drain valve it, whereupon the pressure of the inertgas maintained within the pump tank will cause the leakage oil in space-6!- to be evacuated through conduit 69. This arrangement insures that nooil can enterthe' pump tank 3|.

Located immediately above the sealing assembly is an additional heatdissipating member in the form of a centrifugal impeller 86: This may bepressed, keyed, or'otherwise secured to shaft 5 and defines aplurality-of radially extending air pumping passages 81 having downwardly opening inlet' portions 88. The upper portion of impeller 85'defines a circumferential portion 89 extending radially beyond thedischarge" portion 'ofth'e pumping passages" 81' and having'an outwardlyand downwardly" extending sharp-edged circumference 96, the function ofwhich will be seen hereinafter. It will be apparent'from' Fig.- 3, thatthe action of impeller 86 is to'draw cooling air in as indicated byarrow 9i and discharge it forcefully past the sharp edge 90, asindicated by arrow 92. Any lubricating oil leaking downwardly from thebearing assembly I will run radially outward along the curved uppersurface of impeller 8Buntil it reachesthe sharp-dischargeedge 90-. Atthis point, centrif ugal' force will throw it off the impeller; andthablast' of air '92 will-carry away the oil parti- 7 cles so theycannot land on the upper surface of plate 60.

The primary function of the circulating air 9|, 92 is to further extractany heat passing by conduction along the shaft 5, but, as indicatedabove, it also serves the function of carrying away oil leaking downfrom the bearing assembly 1. Oil thrown from the sharp discharge edge 90of impeller 86 will drain down the irmer surfaces of the motor stand 2and leave through the slots 86.

It will be apparent from the above description of the structure that theflow of heat from the pump housing upwardly into the seal and bearingassemblies is resisted first by the radiation shields 39, 4|, then bythe coolant liquid in the chamber 56, some of the heat which passesthese barriers being extracted in the lubricating oil leaking past thesealing ring I3, and a last increment of heat being extracted by theair-cooled impeller 86. These expedients cooperate to insure that acomparatively small amount of heat reaches the shaft sealing assemblies,and that an even smaller amount of heat will reach the lower bearingassembly 1. Thus, both the seal and bearings are permitted to operate attemperatures well within their safe operating range.

In operation, cooling and lubricating oil is supplied to the port 85 ata pressure on the order of 2 pounds per square inch less than the gaspressure maintained within tank 3!. This is to prevent excessive leakageof oil into tank 3! in the event of seal failure. Also cooling fluid iscirculated at an appropriate rate to the inlet conduit 51. Then when thepump impeller shaft rotates, cooled liquid at substantially pumpdischarge pressure circulates through the bleed line 45 and heatexchanger 46 to the shaft cooling coil 42a, while the centrifugal airimpeller 86 removes whatever increment of heat may travel along theshaft before it can reach the lower bearing 1. All leakage of thehazardous liquid being pumped is collected within the tank 3! andreturned to the closed storage tank 3211, from which it may be drawn offat intervals, purified if necessary, and returned to the pumpingcircuit. The inert pressurizing gas from the reservoir 3|a preventsin-leakage of air from the ambient atmosphere and provides the pressurefor periodically blowing out the oil collecting in the annular passage61', by actuation of the hand valve 10.

With the construction described, the extremely complex cooling and shaftseal assemblies just above the floor plate 3 are in the open and readilyaccessible for inspection and servicing. The plate 60 is convenientlymade in two or more segments so that by removing threaded. fastenings 6!the plate 66 may be removed for access to the upper seal assembly 15.When it becomes necessary to inspect or service the pump impeller,casing, or shaft cooling coil, the tank 3| is readi 1y removed foraccess to the flanged joints securing the inlet elbow I! to the inletpipe and pump discharge scroll respectively.

Thus it will be seen that the invention provides a novel pumpconstruction particularly adapted to be incorporated in a sealed systemhandling a dangerous. liquid, the escape of which must be absolutelyprevented, while at the same time preventing excessive heat from theliquid reaching the shaft seal and bearing assembles.

While only one specific embodiment of the invention has been describedherein, it will be obvious to those skilled in the art that manymodifications may be made, and mechanical equivalents substituted forthe components disclosed herein, and it is desired to cover by theappended claims all such modifications as fall within the true spiritand scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A centrifugal pump comprising bearing means supporting a verticallydisposed shaft having an impeller at the extreme lower end thereof inoverhung relation to the bearing and axially spaced therefrom, a floorplate member disposed in a plane normal to the shaft between impellerand bearing and having a central opening through which the shaftprojects, shaft seal means surrounding the shaft and closing the radialclearance space between shaft and plate, a substantially cylindricalpump frame member having an upper open end portion with a radiallyextending bolting flange secured to the impeller side of the floorplate, an impeller discharge scroll member secured to the lower end ofthe pump frame member and surrounding the impeller, the inner' diameterof the scroll being greater than the tip diameter of the impeller, apump intake casing member comprising an annular disk member forming theinlet side of the impeller chamber and secured at its circumference tothe discharge scroll, the intake casing also having an elbow conduitconnected to the annular disk member with a bolting flange at the endremote from the impeller, said last-mentioned flange being disposedparallel to the axis of the impeller and spaced transversely therefrom,an intake pipe having at the lower end thereof an elbow portion with abolting flange adapted to be secured to the intake casing flange, theother end portion of the intake pipe extending vertically through anopening in the floor plate with substantial radial clearancetherebetween, flexible sealing means disposed in said last-mentionedclearance space and secured to floor plate and pipe whereby differentialthermal expansion between pipe and casing may take place relative to thefloor plate without imposing excessive bending stresses on the pipe, a.discharge pipe member having at the lower end thereof a bolting flangesecured to the discharge flange of the pump scroll, the other end of thedischarge pipe extending vertically upward through an opening in thefloor plate with substantial radial clearance and having flexibleannular sealing means for permitting differential thermal expansionbetween pipe and floor plate, and an open-topped tank surrounding thepump casing and associated conduits, the upper portion of the tankdefining a flange secured to the floor plate and the lower portion ofthe tank defining a sump for collecting any leakage fluid draining fromthe pump casing and conduits.

2. In a machine having a sealed housing with means for maintaining asuper-ambient pressure within the housing and a vertically disposedrotatable shaft projecting through an opening in one wall thereof, thecombination of a shaft seal assembly comprising a cylindrical wallportion having at the lower end thereof a radially extending wall with acircumferental portion adapted to be secured to a wall of the machinehousing, the upper cylindrical portion of the shaft seal housing beingradially spaced from the shaft to define an annular chamber, axiallyspaced upper and lower shaft seal ring assem blies disposed in saidannular chamber and having at the adjacent sides thereof parallelopposed carbon packing rings, a sealing sleeve member having an upperend portion secured to the shaft and a lower cylindrical skirt portiondefining an annular clearance space with the shaft and extendingdownwardly below the lower seal ring, a cylindrical shield member havinga lower end portion secured to the inner circumference of said radiallyextending wall, the shield member extending upwardly in telescopicrelation Within said skirt and being radially spaced therefrom and fromthe shaft, the shield member cooperating with the shaft seal housing todefine an annular drain chamber into which projects the lower endportion of the sealing sleeve skirt, a rotating seal ring member securedto the sealing sleeve and having parallel upper and lower radiallyextending surfaces engaged by the respective carbon rings of the sealring assemblies, means for supplying cooling and lubricating oil to theannular chamber between the seal ring assemblies, drain conduit meanscommunicating with said annular chamber whereby oil may be circulatedfor removing a substantial amount of heat from the shaft and sealassemblies, the annular drain chamber defined by the cylindrical shieldserving to collect the oil which passes the lower carbon ring, drainconduit means communicating with the lowermost portion of said annulardrain chamber and having valve means for removing oil therefrom by theaction of the gas pressure within the pump enclosure tank, whichpressure is communicated through the clearance spaces between the shaftand the cooperating shield and skirt portions of the seal assembly.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,876,520 Newkirk et a1 Sept. 6, 1932 1,898,278 Weis Feb. 21,1933 1,910,811 Peterson May 23, 1933 1,999,163 Allen Apr. 23, 19352,017,026 Forrest et al Oct. 8, 1935 2,075,895 Harmon Apr. 6, 19372,215,449 Alexander et a1. Sept. 24, 1940 2,246,868 Trask June 24, 19412,320,708 Yost June 1, 1943 2,461,821 Howard et al Feb. 15, 1949

